Recently, in order to overcome the deficiencies of a compressor employing a rotating crank shaft, there has been developed a linear type compressor for reciprocally moving a piston using a magnet and a coil instead of a crankshaft, whereby the number of components and the manufacturing cost can be reduced, resulting in an improvement in productivity. Simultaneously, the motor efficiency has been enhanced up to more than 90%, and the electrical consumption has been diminished.
In a typical linear compressor according to the conventional art, as shown in FIG. 1, a cylinder 2 is provided having a predetermined space from an inner bottom surface of an enclosed container 1.
Inside the cylinder, coil assemblies 3,3' are formed to be integral with the cylinder 2.
At a portion of the cylinder 2, a piston spring 4 is fixed, and a piston 5 is connected to an inner central portion of the piston spring 4, which connection enables the piston 5 to make a linear reciprocable movement within the cylinder 2.
A magnet 6 is affixed to an outer circumferential surface of the piston 5, and a plurality of mountain springs 7 are connected between the piston spring 4 and the enclosed container 1 to resiliently support the piston spring 4.
A valve assembly 8 is affixed on a central portion of one end of the cylinder 2, and an intake muffler 9 and an exhaust muffler 10 are affixed to respective sides of the valve assembly 8.
In the above-described linear compressor according to the conventional art, the coil assembly 3,3' affixed to the cylinder 2 and the magnet 6 affixed to the piston 5 carry out a function of a linear motor.
That is, by electromagnetic energy and a resilient force, the piston 5 repeatedly carries out a linear reciprocating movement inside the cylinder 2, and thereby draws a refrigerant through an intake valve comprising the valve assembly 8, and compresses the refrigerant in a compression chamber (C), and then discharges the compressed refrigerant through an exhaust valve.
Here, the intake muffler 9 and the exhaust muffler 10 respectively provided at an intake side and an exhaust side reduce noise in the refrigerant.
In the above-described conventional linear compressor, the opening-closing portions of the valves controlling the flow of the refrigerant are a basic factor in improving the efficiency of the compressor. Therefore, in order to enhance the efficiency of the compressor, there is known an axial flow valve system which has the same flow direction of the refrigerant as the movement direction of the piston.
In an inertia-mode(for opening and closing the intake valve using inertia) valve system employed in the conventional linear compressor, as shown in FIG. 2, a cylindrical groove 2a is provided in a portion of an inner circumferential surface of the cylinder 2A.
In addition, at a central front portion of the piston 5A, an intake valve 11 is affixed with a caulking by a piston pin 12. Here, the intake valve 11 is disposed to be moved to the left and right, and therefore can control the flow of the refrigerant in accordance with the movement direction of the piston 5A.
A head cover 13 is connected to one end of the cylinder 2A, and an exhaust valve 14 and a spring 15 are disposed inside the head cover 13. Therefore, when the pressure of the refrigerant gas compressed in the compression chamber (C) of the cylinder 2A exceeds the resilient force of the spring 15, the refrigerant pushes open the exhaust valve 14, and then is exhausted through the head cover 13.
Reference numeral 5b denotes a threaded hole for receiving the threaded pin 12, reference numeral 11a denotes a pin hole in the intake valve 11, and reference numeral 13a denotes a refrigerant exhaust pipe disposed in the head cover 13.
In the inertia-mode valve apparatus for the conventional linear compressor, in the intake cycle the refrigerant is sucked into the piston 5A through the refrigerant intake port 2b of the cylinder 2A and the piston groove 5a when the piston 5A is moved away from the exhaust valve 14 in the intake cycle, and since the intake valve 11 is opened by inertia, the refrigerant flows in between the intake valve 11 and the piston 5A and into the compression chamber (C).
Here, movement of the intake valve 11 beyond a predetermined distance is limited by the piston pin 12.
Then, as shown in FIG. 3, when the compression cycle is performed, the refrigerant in the compression chamber (C) is compressed and thereby the pressure on the exhaust valve 14 exceeds the force of the spring and the valve 14 is moved away from the piston 5A, resulting in the exhausting of the compressed refrigerant through the refrigerant exhaust pipe 13a of the head cover 13. Here, the intake valve 11 is closely contacted with the front surface of the cylinder 2A and therefore the minimum clearance volume is maintained.
After the above-described compression cycle, as shown in FIG. 4, as the piston 5A moves away from the exhaust valve 14, the intake valve 11 is distanced from the front surface of the piston 5A, and then the above-described intake cycle is repeated. Here, the exhaust valve 14 is returned to its initial condition by the restoring force of the spring 15.
FIGS. 5 through 8 shows a valve apparatus for a linear compressor according to the conventional art, and a first exhaust valve 14A and a second exhaust valve 14B, namely a closing member for the first exhaust valve, inside the head cover 13 are illustrated.
At a central portion of the first-exhaust valve 14A, as shown in FIG. 7, a refrigerant exhaust port 14a is formed, and as shown in FIG. 8, the second exhaust valve 14B is formed in a spiral shape for opening and closing the refrigerant exhaust port 14a of the exhaust valve 14A.
The same elements as in FIG. 2 are indicated by the same reference numerals.
In this other axial flow valve apparatus for a linear compressor according to the conventional art, after the refrigerant is sucked into the piston 5A through the refrigerant intake port 2b of the cylinder 2A and the cylinder groove 2a, and flows in between the piston 5A and the intake valve 11 to fill the compression chamber (C).
Here, since the intake valve 11 is fixed to the piston 5A by the piston pin, the valve 11 may not move beyond a predetermined distance.
Then, when the piston 5A is moved in the direction of the first exhaust valve 14A and the compression cycle is performed, the compressed refrigerant flows into the exhaust port 14a of the first exhaust valve 14A.
Here, as shown in FIGS. 7 and 8, when the piston pin 12 is inserted in the exhaust port 14a of the first exhaust valve 14A during the compression stroke, the central portion of the second exhaust valve 14B is pushed open and the compressed refrigerant is exhausted through the refrigerant exhaust pipe 13a of the head cover 13.
That is, the second exhaust valve 14B is opened and closed on its own, resulting in a prompt opening and closing of the valve 14B.
Here, when the front end of the piston 5A contacts with the first exhaust valve 14A, the force of the spring 15 is applied to the first exhaust valve 14A and the second exhaust valve 14B, resulting in the stable operation of the exhaust valves.
But, in the axial flow valve apparatus for the linear compressor according to the conventional art, in the case of the former apparatus, since the exhaust valve 14 is resiliently supported by the spring 15, when the exhausting of the compressed refrigerant is performed, the opening and closing of the exhaust valve proceeds slowly, and the intake valve 11 may stick to the front surface of the piston 5A due to the pressure of oil used for the lubrication of the piston 5A, and friction may be produced between the intake valve 11 and the piston pin 12, or the repeated movement of the intake valve 11 may disadvantageously cause the diameter of the pin hole 11a of the intake valve 11 integral with the piston pin 12 to become gradually larger. Consequently, the operation of the intake valve 11 may become unstable, and the efficiency of the linear compressor may become lowered.
And, in the case of the latter conventional linear compressor, the double exhaust valve construction using the first exhaust valve 14A and the second exhaust valve 14B is employed, and as a result, a prompt opening and closing of the exhaust valve is preferably carried out. However, since the intake valve is moved by the axial flow, defects caused by the oil in the former apparatus cannot be overcome, and since the second exhaust valve 14B is in the shape of a resilient thin film and much displacement occurs therein during the exhaust of the refrigerant, if the valve 14B is used for an long time, the reliability of the valve operation can become lowered.